Lifecycle Methods

Lifecycle Methods Overview

Lifecycle Methods is a building block you will reach for often in single-spa. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn lifecycle methods properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real single-spa projects.

export async function bootstrap(props) {
  // one-time setup
}

export async function mount(props) {
  // render the app into props.domElement
}

export async function unmount(props) {
  // tear down and clean up
}

Every single-spa application exports bootstrap, mount, and unmount lifecycle functions.

Lifecycle Methods Example

registerApplication({
  name: '@org/app',
  app: () => System.import('@org/app'),
  activeWhen: ['/app'],
});
start();

• Start from a minimal Lifecycle Methods example and grow it only as needed.
• Keep configuration explicit so Lifecycle Methods behaves the same in every environment.
• Name things clearly so teammates understand your Lifecycle Methods at a glance.
• Add tests around Lifecycle Methods early to lock in expected behaviour.

Single-SPA Cheatsheet

Core single-spa APIs related to lifecycle methods.

How Lifecycle Methods Works in Single-SPA

Lifecycle Methods is part of how single-spa lets multiple applications — even in different frameworks — coexist on one page. A root config registers each app and controls when it is active.

Every single-spa application exports bootstrap, mount, and unmount lifecycle functions.

• A root config registers apps and calls start().
• Each app exports bootstrap, mount, and unmount lifecycles.
• activeWhen decides which routes each app owns.
• Import maps resolve each app's bundle at runtime.

Practical Guidance for Lifecycle Methods

For reliable micro frontends, lifecycle methods should isolate failures and keep shared state minimal. Let each team own its app end to end while agreeing on a few shared contracts.

Common Mistakes

• Copying lifecycle methods snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up lifecycle methods.
• Leaving lifecycle methods untested, so regressions slip into production.
• Over-engineering lifecycle methods before you actually need the extra flexibility.

Key Takeaways

• Lifecycle Methods is a core part of working effectively with single-spa.
• Start small and keep lifecycle methods focused on a single responsibility.
• Apply consistent patterns so lifecycle methods scales across your project.
• Test and document lifecycle methods to keep it maintainable over time.